Windows: Prevent white flicker when showing main window (#9637)

* Fixes #9603

src/gui/MainWindow.cpp

@@ -707,13 +707,6 @@ MainWindow::~MainWindow()
  */
 void MainWindow::restoreConfigState()
 {
-    // start minimized if configured
-    if (config()->get(Config::GUI_MinimizeOnStartup).toBool()) {
-        hideWindow();
-    } else {
-        bringToFront();
-    }
-
     if (config()->get(Config::OpenPreviousDatabasesOnStartup).toBool()) {
         const QStringList fileNames = config()->get(Config::LastOpenedDatabases).toStringList();
         for (const QString& filename : fileNames) {
@@ -1370,6 +1363,24 @@ void MainWindow::databaseTabChanged(int tabIndex)
     updateEntryCountLabel();
 }
 
+void MainWindow::showEvent(QShowEvent* event)
+{
+    Q_UNUSED(event)
+#ifdef Q_OS_WIN
+    // Qt Hack - Prevent white flicker when showing window
+    QTimer::singleShot(50, this, [=] { setProperty("windowOpacity", 1.0); });
+#endif
+}
+
+void MainWindow::hideEvent(QHideEvent* event)
+{
+    Q_UNUSED(event)
+#ifdef Q_OS_WIN
+    // Qt Hack - Prevent white flicker when showing window
+    setProperty("windowOpacity", 0.0);
+#endif
+}
+
 void MainWindow::closeEvent(QCloseEvent* event)
 {
     if (m_appExiting) {

src/gui/MainWindow.h

@@ -96,6 +96,8 @@ public slots:
     void restartApp(const QString& message);
 
 protected:
+    void showEvent(QShowEvent* event) override;
+    void hideEvent(QHideEvent* event) override;
     void closeEvent(QCloseEvent* event) override;
     void changeEvent(QEvent* event) override;
     void keyPressEvent(QKeyEvent* event) override;

src/main.cpp

@@ -182,6 +182,10 @@ int main(int argc, char** argv)
     Application::bootstrap();
 
     MainWindow mainWindow;
+#ifdef Q_OS_WIN
+    // Qt Hack - Prevent white flicker when showing window
+    mainWindow.setProperty("windowOpacity", 0.0);
+#endif
 
     // Disable screen capture if not explicitly allowed
     // This ensures any top-level windows (Main Window, Modal Dialogs, etc.) are excluded from screenshots
@@ -203,6 +207,14 @@ int main(int argc, char** argv)
         mainWindow.openDatabase(filename, password, parser.value(keyfileOption));
     }
 
+    // start minimized if configured
+    if (config()->get(Config::GUI_MinimizeOnStartup).toBool()) {
+        mainWindow.hideWindow();
+    } else {
+        mainWindow.bringToFront();
+        Application::processEvents();
+    }
+
     int exitCode = Application::exec();
 
     // Check if restart was requested